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  • Case ID: 330750
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I am using nRF5340 Audio to make a CIS connection on a homemade board.

Junichi

I am aiming to connect the Gateway and Headset 1:1 and output stereo from the Headset.

The Gateway side is 16-bit I2S and the Headset side is 32-bit I2S, and I am able to output sound from the Headset in mono.

The I2C compatible ICs for both the Headset and Gateway are stereo compatible.

After referring to various answers on Devzone, I have reached a point where I can connect BLE but cannot achieve synchronization.

I have confirmed that the I2S waveforms of the three types of clocks are available on both the Gateway and Headset.

If the values ​​of CONFIG_BT_AUDIO_BITRATE_UNICAST_SINK and CONFIG_BT_AUDIO_BITRATE_UNICAST_SRC are between 72000 and 80000, BLE can be connected, but if they are 96000, BLE cannot be connected.

What could be the reason for the lack of sync?

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  • 0

    Hi, 

    What NCS version are you using? Could you try the latest version v2.7.0?

    We are currently understaffed due to the summer vacation period, so delayed replies must be expected. I am sorry about any inconvenience this might cause.

    Regards,
    Amanda H.

  • 0 in reply to Amanda Hsieh

    NCS version is 2.5.0

    It's running in mono and I want to make it work with this version.

  • 0 in reply to Junichi

    Hi, 

    The reason why the higher bitrate causes the sync mechanism not to work properly might be because the enc/dec time increased. The team suggests to extend the presentation delay configuration. NCS v2.5.0 uses the deprecated PCFT controller which we won't support anymore. Please switch to the latest NCS which uses the SoftDdevice Controller. 

    And since the description from the customer is not very clear, some more details

    • If the gateway can connect with headsets and do the audio streaming but cannot have steady pres/drift compensation, then that could be because the CPU consumes too much time
    • Please provide the application log if the gateway cannot establish an audio stream. It might be the config setting out of what the controller/bandwidth can achieve, then it has to reduce the retransmission times for a trial.
    • The 96kbps is the default setting as we tested it, and you also mentioned that you are working on the stereo channel.
      It could be that you are trying to send L and R at the same ISO packets, which leads to a 240-byte encoded frame in one ISO packet, which could reach the limitation of the PCFT controller.
      We will support CIS stereo in the following time which headset can receive L and R from different CISes, please stay tuned.
      And please upgrade the code to the latest NCS.

    -Amanda H.

Reply
  • 0 in reply to Junichi

    Hi, 

    The reason why the higher bitrate causes the sync mechanism not to work properly might be because the enc/dec time increased. The team suggests to extend the presentation delay configuration. NCS v2.5.0 uses the deprecated PCFT controller which we won't support anymore. Please switch to the latest NCS which uses the SoftDdevice Controller. 

    And since the description from the customer is not very clear, some more details

    • If the gateway can connect with headsets and do the audio streaming but cannot have steady pres/drift compensation, then that could be because the CPU consumes too much time
    • Please provide the application log if the gateway cannot establish an audio stream. It might be the config setting out of what the controller/bandwidth can achieve, then it has to reduce the retransmission times for a trial.
    • The 96kbps is the default setting as we tested it, and you also mentioned that you are working on the stereo channel.
      It could be that you are trying to send L and R at the same ISO packets, which leads to a 240-byte encoded frame in one ISO packet, which could reach the limitation of the PCFT controller.
      We will support CIS stereo in the following time which headset can receive L and R from different CISes, please stay tuned.
      And please upgrade the code to the latest NCS.

    -Amanda H.

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